Field
Implementations of the present disclosure generally relate to apparatus for etching of substrates during semiconductor manufacturing.
Description of the Related Art
Chip manufacturers strive for high device yield, low defect count, and increased performance from every wafer processed for increased efficiency. Device yield per wafer can be increased by maximizing patterned area on each substrate while maintaining or reducing defect count.
The bevel edge of the wafer needs to be cleaned to avoid bevel peeling and reduce defect count and further contamination of the wafer in the lithography tool. The area near the bevel edge where no deposition is desired to avoid bevel peeling is termed “edge-exclusion”. The deposition region within the edge exclusion is ideally a film with uniform thickness over the wafer surface. However, due to plasma behavior at the bevel edge of the wafer for some deposition materials such as amorphous carbon, the film can be thicker at the edge resulting in an “edge-hump”.
The current approach is to use a shadow ring to cover the edge of the wafer to reduce the thickness of the edge-hump and to keep the bevel clean. The limitation of this approach is that the edge exclusion zone extends to 3.5 mm and is detrimental to device yield. The edge profile is also not easily customizable as it is dependent on the size and shape of the shadow ring. The current shadow ring based approach has had only limited success creating bevel edge exclusion lengths of less than 3.5 mm.
FIG. 1A (Prior Art) is a partial cross-sectional view showing an ideal profile for a deposition layer 102 formed on a substrate 101. The deposition layer 102 is uniformly deposited across a top surface of the substrate 101 and there is no deposition within an edge exclusion area 103. However, an actual deposition profile generally differs from the ideal configuration illustrated in FIG. 1A. FIG. 1B (Prior Art) is a partial cross-sectional view showing an actual surface profile of a deposition layer 102a on the substrate 101 after having undergone a CVD or PECVD deposition. The deposition layer 102a is deposited without the use of a shadow frame or other edge deposition control. Shown here, the deposition layer 102a extends to the edge exclusion area 103. A bevel edge 104 with extra thickness may be formed near the edge exclusion area 103.
To prevent the formation of the deposition film at the edge of the substrate, FIG. 1C (Prior Art) is a partial cross-sectional view showing one conventional approach that proposes to use a shadow ring 105. The shadow ring 105 is usually arranged at a location that overlaps and covers at least one portion of the edge exclusion area 103 of the substrate 101. As a result, as shown in FIG. 1C, a deposition layer 102b gradually reduces under the shadow of the shadow ring 105. The gradual reduction of the deposition layer 102b leaves non-level deposition product over edge exclusion area 103 and a portion of the preceding area of the deposition layer 102b. 
Therefore, there is a need for devices and methods for further reducing bevel edge exclusion.